The French interior minister, Nicolas Sarkozy, yesterday described the abduction, torture and killing of a young Jewish man as an anti-Semitic crime, amid growing anger at the brutal murder.

Mr Sarkozy told the French parliament that the gang sought for the murder of Ilan Halimi, 23, whose naked body was found by railway tracks eight days ago, three weeks after he had disappeared, had also tried to kidnap other Jews.

The police, who found literature linking some of the suspects to Palestinian and Muslim groups, have insisted the murder was motivated by greed - the gang had demanded a ransom - and not religious motives.

Mr Sarkozy told MPs: "The truth is that these crooks acted primarily for sordid and vile motives, to get money, but they were convinced that 'the Jews have money', and if those they kidnapped didn't have money, their family and their community would come up with it.

"That's called anti-Semitism by amalgam."

He added that four of the six other people the gang had approached and tried to kidnap "were of the Jewish faith" and described the criminals as "barbaric".

The judge overseeing the inquiry into the murder has instructed investigators to look into anti-Semitic motives in the cases of seven of the 13 suspects arrested.

Mr Sarkozy added: "We have a duty to the memory of Ilan Halimi, to his family, his parents, his friends and above all, all the Jews of France, to establish the truth."

Ilan Halimi was snatched on January 21. A young woman, suspected as acting as a lure, has since given herself up. His family received numerous ransom demands. He was found, with 80% of his body burned, naked and handcuffed on February 13. He died on the way to hospital.

Mr Sarkozy said he was releasing details of the inquiry but he hoped they would not arouse hate or fear. "What we don't need now, in addition to this barbarity, is misunderstanding, intolerance and racism," he said.

France's Jewish community numbers around 600,000, the Muslim community around five million, both the largest in Europe.

Two French police officers flew to Ivory Coast yesterday on the trail of Youssef Fofana, the suspected gang leader who had reportedly flown back to his native country after the murder. According to police, Mr Fofana had called himself the "brain of the barbarians".

Police had earlier insisted the murder was not anti-Semitic, but the victim's mother Ruth Halimi accused them of ignoring this motive for fear of upsetting Muslim opinion.

She told the Israeli newspaper Ha'aretz that if her son "hadn't been Jewish, he wouldn't have been killed".

"We told the police there were at least three attempted kidnappings of young Jews but they kept insisting that the motives were purely criminal."

Jean-Claude Marin, the Paris public prosecutor, told Le Monde yesterday: "When the legal case was opened the anti-Semitic nature of the crime did not come up at all.

"Then, during the weekend, certain people interviewed let it be known, in an indirect way, that the choice of a Jew guaranteed the payment of a ransom. The judge therefore considered that there was possibly an anti-Semitic motive."

According to Le Parisien the woman who had tried to lure two men into the gang's clutches admitted to police that she was instructed to target Jewish men.

"In the heads of these youngsters the [Jewish] community had the solidarity to rapidly collect a ransom. The gang wanted money so they went out to get it where they thought they'd find it," a source close to the inquiry told the newspaper.

When the kidnapped man's family told the gang they could not find the €450,000 (£315,000) they had demanded they were told to "go and ask in the synagogues", the newspaper added.